Semiconductor light emitting device

ABSTRACT

A semiconductor light emitting device includes a conductive substrate and a first metal layer disposed on the substrate. The first metal layer is formed so as to be electrically connected with the substrate, and the first metal layer includes an Au based material. A joining layer is formed on the first metal layer. The joining layer includes a second metal layer including Au and a third metal layer including Au. A metallic contact layer and an insulating layer are formed on the joining layer. A semiconductor layer is formed on the metallic contact layer and the insulating layer and includes a red-based light emitting layer. An electrode is formed on the semiconductor layer and is made of metal. The insulating layer includes a patterned aperture, and at least a part of the metallic contact layer is formed in the aperture.

This application is a continuation of application Ser. No. 15/248,332,filed on Aug. 26, 2016, and allowed on Jun. 8, 2017, which is acontinuation of application Ser. No. 14/928,349, filed on Oct. 30, 2015(issued on Sep. 20, 2016 as U.S. Pat. No. 9,450,145), which is acontinuation of application Ser. No. 14/286,696, filed on May 23, 2014(issued on Nov. 24, 2015 as U.S. Pat. No. 9,196,808), which is in turn adivisional application of U.S. application Ser. No. 14/024,696, filed onSep. 12, 2013 (issued on Apr. 28, 2015 as U.S. Pat. No. 9,018,650),which is a divisional application of Ser. No. 13/327,860, filed on Dec.16, 2011 (issued on Sep. 17, 2013 as U.S. Pat. No. 8,536,598), which isa divisional application of Ser. No. 12/596,004, filed on Oct. 15, 2009(issued on Jan. 31, 2012 as U.S. Pat. No. 8,106,412), which is aNational Stage application of PCT/JP2008/057176, filed on Apr. 11, 2008.The prior U.S. applications and the present application claim thebenefit of priority of Japanese application Serial No. JP 2007-107130,filed on Apr. 16, 2007. The contents of these prior applications areincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a semiconductor light emitting deviceand a fabrication method for the same, and in particular, relates to asemiconductor light emitting device formed for bonding a light emittingdiode having a metallic reflecting layer, and a non-transparentsubstrate layer by wafer bonding technology, and a fabrication methodfor the same.

BACKGROUND ART

A structure which forms a metallic reflecting layer as an opticalreflecting layer between a substrate and an active layer composed of anMQW (Multi-Quantum Well) layer is proposed in order to perform the highbrightness of an LED (Light Emitting Diode). As a method of forming sucha metallic reflecting layer, the wafer bonding technology of a substrateof a light emitting diode layer is disclosed in Patent Literature 1 andPatent Literature 2, for example.

In Patent Literature 1 and Patent Literature 2, the purpose is toprovide a fabrication method of a light emitting diode which canfabricate a light emitting diode having a desired mechanicalcharacteristic and optical transparency, and can make a minimum specificresistance of boundary surface between a transparent layer and a growthlayer; and it is characterized by fabricating the light emitting diodeby removing a temporary growth substrate after growing up a lightemitting diode layer one after another on the temporary growth substrateand forming a light emitting diode structure having a relatively thinlayer, and wafer-bonding a conductive and optical transparent substrateon the light emitting diode layer which becomes a buffer layer of lowerlayer on the position instead of the temporary growth substrate.

In Patent Literature 1 and Patent Literature 2, transparent materials,such as GaP and sapphire, are applied to the substrate used for thewafer bonding.

-   Patent Literature 1: Japanese Patent Application Laying-Open    Publication No. H06-302857-   Patent Literature 2: U.S. Pat. No. 5,376,580

A schematic cross-section structure of a conventional semiconductorlight emitting device formed by the wafer bonding technology isexpressed as shown in FIG. 23 to FIG. 25.

For example, as shown in FIG. 23, a conventional semiconductor lightemitting device includes: an Au—Sn alloy layer 14 disposed on a GaAssubstrate 15; a barrier metal layer 13 disposed on the Au—Sn alloy layer14; a p type cladding layer 10 disposed on the barrier metal layer 13;an MQW layer 9 disposed on the p type cladding layer 10; an n typecladding layer 8 disposed on the MQW layer 9; and a window layer 7disposed on the n type cladding layer 8.

In the conventional semiconductor light emitting device shown in FIG.23, the metal used for the wafer bonding is Au—Sn alloy. As for theAu—Sn alloy, since the melting point is low, the Au—Sn alloy at the sideof an epitaxial growth layer composing an LED in low temperature, andthe Au—Sn alloy at the side of the GaAs substrate 15 can be melted andbonded.

However, since the thermal diffusion of Sn occurs when using the Au—Snalloy layer 14, in order to prevent the diffusion of Sn, as shown inFIG. 23, it is necessary to insert the barrier metal layer 13. Moreover,there is a problem that the Au—Sn alloy layer 14 has a wrong opticalreflection factor.

For example, as shown in FIG. 24, another conventional semiconductorlight emitting device includes: a metallic reflecting layer 16 disposedon a GaAs substrate 15; a p type cladding layer 10 disposed on themetallic reflecting layer 16; an MQW layer 9 disposed on the p typecladding layer 10; an n type cladding layer 8 disposed on the MQW layer9; and a window layer 7 disposed on the n type cladding layer 8. In theconventional semiconductor light emitting device shown in FIG. 24, thereis a problem that light cannot be efficiently reflected in the metallicreflecting layer 16 fabricated by bonding the GaAs substrate 15 sincethe optical absorption occurs in the interface between metal and asemiconductor. That is, there is a problem that the optical absorptionoccurs in the interface between the p type cladding layer 10 and themetallic reflecting layer 16.

In order to perform high brightness of the semiconductor LED (LightEmitting Device), there is also a method of inserting a DBR (DistributedBragg Reflector) layer between the GaAs substrate and the active layer(MQW) as an optical reflecting layer. The LED of the structure whichdoes not insert the DBR becomes dark since the light which emitted inthe MQW layer is absorbed by the GaAs substrate. Therefore, in order toperform the high brightness of the LED using the GaAs substrate, the DBRis used as the optical reflecting layer.

That is, as shown in FIG. 25, another conventional semiconductor lightemitting device includes: a DBR layer 19 disposed on a GaAs substrate15; a p type cladding layer 10 disposed on the DBR layer 19; an MQWlayer 9 disposed on the p type cladding layer 10; an n type claddinglayer 8 disposed on the MQW layer 9; and a window layer 7 disposed onthe n type cladding layer 8. In the conventional semiconductor lightemitting device shown in FIG. 25, the DBR layer 19 is used as an opticalreflecting layer between the GaAs substrate 15 and the MQW layer 9.There is a problem that the DBR layer 19 reflects only an incident lightfrom a certain one way, the DBR does not reflect light if an incidentangle changes, and the DBR layer 19 does not reflects an incident lightfrom other angle and then passes through the incident light. Therefore,there is a problem that the passed through light is absorbed by the GaAssubstrate 15 and the light emitting brightness of the semiconductor LED(Light Emitting Device) is reduced.

The conventional semiconductor light emitting device formed by the waferbonding technology needs to insert the barrier metal layer, in order toprevent the thermal diffusion of Sn, when using the Au—Sn alloy layer asa metal used for the wafer bonding. Moreover, the Au—Sn alloy layer hasa wrong optical reflection factor.

Moreover, even if the metallic reflecting layer is formed by bonding thesubstrate, the optical absorption occurs in the interface between themetal and the semiconductor, and then the light cannot be reflectedefficiently.

Moreover, when the DBR layer is used as the reflecting layer, the DBRlayer reflects only an incident light from a certain one way, the DBRlayer does not reflect and passes through the incident light if anincident angle changes, and the incident light is absorbed by the GaAssubstrate, thereby the light emitting brightness of LED is reduced.

Then, the purpose of the present invention is to provide a semiconductorlight emitting device with the high luminance formed by performing thewafer bonding of the substrate using a non-transparent semiconductorsubstrate, such as GaAs and Si, and forming the metallic reflectinglayer, and a fabrication method for the same.

Moreover, the purpose of a present invention is to provide asemiconductor light emitting device with the high luminance formed byavoiding the contact between a semiconductor and metal, preventing theoptical absorption in the interface between the semiconductor and themetal, and forming the metallic reflecting layer having a sufficientreflection factor, by inserting a transparent insulating film betweenthe metal and the semiconductor, and a fabrication method for the same.

Moreover, the purpose of the present invention is to provide asemiconductor light emitting device with the high luminance whichbecomes possible to reflect the light of all angles by using not the DBRbut a metal layer for the optical reflecting layer, and a fabricationmethod for the same.

SUMMARY OF INVENTION

One aspect of the semiconductor light emitting device of the presentinvention for achieving the above-mentioned purpose is characterized bycomprising: a GaAs substrate structure including a GaAs layer, a firstmetal buffer layer disposed on a surface of the GaAs layer, a firstmetal layer disposed on the first metal buffer layer, a second metalbuffer layer disposed at a back side of the GaAs layer, and a secondmetal layer disposed on a surface of an opposite side of the GaAs layerof the second metal buffer layer; and a light emitting diode structuredisposed on the GaAs substrate structure and including a third metallayer, a metal contact layer disposed on the third metal layer, a p typecladding layer disposed on the metal contact layer, a multi-quantum welllayer disposed on the p type cladding layer, an n type cladding layerdisposed on the multi-quantum well layer, and a window layer disposed onthe n type cladding layer, wherein the GaAs substrate structure and thelight emitting diode structure are bonded by using the first metal layerand the third metal layer.

Another aspect of the semiconductor light emitting device of the presentinvention is characterized by comprising: a GaAs substrate; a metallayer disposed on the GaAs substrate; and a light emitting diodestructure including a patterned metal contact layer and a patternedinsulating layer disposed on the metal layer, a p type cladding layerdisposed on the patterned metal contact layer and the patternedinsulating layer, a multi-quantum well layer disposed on the p typecladding layer, an n type cladding layer disposed on the multi-quantumwell layer, and a window layer disposed on the n type cladding layer,wherein the GaAs substrate and the light emitting diode structure arebonded by using the metal layer.

Another aspect of the semiconductor light emitting device of the presentinvention is characterized by comprising: a GaAs substrate structureincluding a GaAs substrate, and a first metal layer disposed on asurface of the GaAs substrate; and a light emitting diode structuredisposed on the aforementioned GaAs substrate structure and including asecond metal layer, a p type cladding layer disposed on the second metallayer, a multi-quantum well layer disposed on the p type cladding layer,an n type cladding layer disposed on the multi-quantum well layer, and awindow layer disposed on the n type cladding layer, wherein the GaAssubstrate and the light emitting diode structure are bonded by using thefirst metal layer and the second metal layer.

Another aspect of the semiconductor light emitting device of the presentinvention is characterized by comprising: a silicon substrate structureincluding a silicon substrate, a titanium layer disposed on the siliconsubstrate, and a first metal layer disposed on the titanium layer; and alight emitting diode structure including a second metal layer disposedon the first metal layer, a patterned metal contact layer and apatterned insulating layer disposed on the second metal layer, anepitaxial growth layer disposed on the patterned metal contact layer andthe patterned insulating layer and having a frosting processing regionon a surface exposed, a patterned n type GaAs layer disposed on theepitaxial growth layer, and a patterned surface electrode layer disposedon the n type GaAs layer, wherein the silicon substrate structure andthe light emitting diode structure are bonded by using the first metallayer and the second metal layer.

Another aspect of the semiconductor light emitting device of the presentinvention is characterized by comprising: a GaAs substrate structureincluding a GaAs substrate, a metal buffer layer disposed on the GaAssubstrate, and a first metal layer disposed on the metal buffer layer;and a light emitting diode structure including a second metal layerdisposed on the first metal layer, a patterned metal contact layer and apatterned insulating layer disposed on the second metal layer, anepitaxial growth layer disposed on the patterned metal contact layer andthe patterned insulating layer and having a frosting processing regionon a surface exposed, a patterned n type GaAs layer disposed on theepitaxial growth layer, and a patterned surface electrode layer disposedon the n type GaAs layer, wherein the GaAs substrate structure and thelight emitting diode structure are bonded by using the first metal layerand the second metal layer.

Another aspect of the fabrication method for the semiconductor lightemitting device of the present invention is characterized by comprising:preparing a semiconductor substrate structure for wafer bonding and alight emitting diode structure for wafer bonding; forming a first metallayer on a semiconductor substrate in the semiconductor substratestructure; forming an AlInGaP layer on a GaAs substrate, an n type GaAslayer, and an epitaxial growth layer one after another in the lightemitting diode structure; forming a metal contact layer and a secondmetal layer for a patterned insulating layer on the epitaxial growthlayer; bonding the semiconductor substrate structure for the waferbonding, and the light emitting diode structure for the wafer bonding bythermocompression bonding; removing the GaAs substrate by etching;removing an AlInGaP layer; performing pattern formation of a surfaceelectrode layer; and removing the n type GaAs layers except the n typeGaAs layer directly under the surface electrode layer by performingfrosting processing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional configuration diagram of a p typeGaAs substrate applied to a semiconductor light emitting device and afabrication method for the same according to a first embodiment of thepresent invention.

FIG. 2 is a schematic cross-sectional configuration diagram of an n typeGaAs substrate applied to the semiconductor light emitting device andthe fabrication method for the same according to the first embodiment ofthe present invention.

FIG. 3 is a schematic cross-sectional configuration diagram of an LEDapplied to the semiconductor light emitting device and the fabricationmethod for the same according to the first embodiment of the presentinvention.

FIG. 4 is a schematic cross-sectional configuration diagram of thesemiconductor light emitting device according to the first embodiment ofthe present invention.

FIG. 5 is a schematic cross-sectional configuration diagram of an LEDapplied to a semiconductor light emitting device and a fabricationmethod for the same according to a second embodiment of the presentinvention.

FIG. 6 is a schematic cross-sectional configuration diagram of an LEDapplied to a semiconductor light emitting device and a fabricationmethod for the same according to a modified example of the secondembodiment of the present invention.

FIG. 7 is a schematic cross-sectional configuration diagram of thesemiconductor light emitting device according to the second embodimentof the present invention.

FIG. 8 is a schematic cross-sectional configuration diagram of a GaAssubstrate applied to a semiconductor light emitting device and afabrication method for the same according to a third embodiment of thepresent invention.

FIG. 9 is a schematic cross-sectional configuration diagram of an LEDapplied to the semiconductor light emitting device and the fabricationmethod for the same according to the third embodiment of the presentinvention.

FIG. 10 is a schematic cross-sectional configuration diagram of thesemiconductor light emitting device according to the third embodiment ofthe present invention.

FIG. 11 is a schematic cross-sectional configuration diagram of an Sisubstrate applied to a semiconductor light emitting device and afabrication method for the same according to a fourth embodiment of thepresent invention.

FIG. 12 is a schematic cross-sectional configuration diagram of an LEDapplied to the semiconductor light emitting device and the fabricationmethod for the same according to the fourth embodiment of the presentinvention.

FIG. 13 is a schematic plane pattern structural drawing of the LEDapplied to the semiconductor light emitting device and the fabricationmethod for the same according to the fourth embodiment of the presentinvention.

FIG. 14 is another schematic plane pattern structural drawing of the LEDapplied to the semiconductor light emitting device and the fabricationmethod for the same according to the fourth embodiment of the presentinvention.

FIG. 15 is a schematic cross-sectional configuration diagram forexplaining one process of the fabrication method of the semiconductorlight emitting device according to the fourth embodiment of the presentinvention.

FIG. 16 is a schematic cross-sectional configuration diagram forexplaining one process of the fabrication method of the semiconductorlight emitting device according to the fourth embodiment of the presentinvention.

FIG. 17 is a schematic cross-sectional configuration diagram forexplaining one process of the fabrication method of the semiconductorlight emitting device according to the fourth embodiment of the presentinvention.

FIG. 18 is a schematic cross-sectional configuration diagram forexplaining one process of the fabrication method of the semiconductorlight emitting device according to the fourth embodiment of the presentinvention.

FIG. 19 is a schematic cross-sectional configuration diagram forexplaining one process of the fabrication method of the semiconductorlight emitting device according to the fourth embodiment of the presentinvention.

FIG. 20 is a schematic cross-sectional configuration diagram forexplaining one process of the fabrication method of the semiconductorlight emitting device according to the fourth embodiment of the presentinvention.

FIG. 21 is a schematic cross-sectional configuration diagram forexplaining one process of a fabrication method of a semiconductor lightemitting device according to a modified example of the fourth embodimentof the present invention.

FIG. 22 is a schematic cross-sectional configuration diagram forexplaining one process of a fabrication method of a semiconductor lightemitting device according to another modified example of the fourthembodiment of the present invention.

FIG. 23 is a schematic cross-sectional configuration diagram of aconventional semiconductor light emitting device.

FIG. 24 is another schematic cross-sectional configuration diagram ofthe conventional semiconductor light emitting device.

FIG. 25 is another schematic cross-sectional configuration diagram ofthe conventional semiconductor light emitting device.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, an embodiment of the invention is described with reference todrawings. In the description of the following drawings, the same orsimilar reference numeral is attached to the same or similar part.However, a drawing is schematic and it should care about differing froman actual thing. Drawings are schematic, not actual, and may beinconsistent in between in scale, ratio, etc.

The embodiment shown in the following exemplifies the device and methodfor materializing the technical idea of the invention, and the technicalidea of the invention does not specify assignment of each componentparts, etc. as the following. Various changes can be added to thetechnical idea of the invention in scope of claims.

First Embodiment

(Element Structure)

It is applicable also in any of a p type and an n type, as aconductivity type of a GaAs substrate applied to a semiconductor lightemitting device and a fabrication method for the same according to afirst embodiment of the present invention.

A schematic cross-section structure of a p type GaAs substrate appliedto the semiconductor light emitting device and the fabrication methodfor the same according to the present embodiment is expressed as shownin FIG. 1. Moreover, a schematic cross-section structure of an n typeGaAs substrate applied to the semiconductor light emitting device andthe fabrication method according to the present embodiment for the sameis expressed as shown in FIG. 2. Moreover, a schematic cross-sectionstructure of an LED applied to the semiconductor light emitting deviceand a fabrication method for the same according to the presentembodiment is expressed as shown in FIG. 3.

A schematic cross-section structure of the semiconductor light emittingdevice according to the present embodiment formed by bonding mutuallythe LED shown in FIG. 3 with the p type GaAs substrate or the n typeGaAs substrate shown in FIG. 1 or FIG. 2 by wafer bonding technology isexpressed as shown in FIG. 4.

As shown in FIG. 1, the p type GaAs substrate applied to thesemiconductor light emitting device and the fabrication method for thesame according to the present embodiment includes: a p type GaAs layer3; a metal buffer layer 2 disposed on the surface of the p type GaAslayer 3; a metal layer 1 disposed on the metal buffer layer 2; a metalbuffer layer 4 disposed at the back side of the p type GaAs layer 3; anda metal layer 5 disposed on the surface of the opposite side at the sideof the p type GaAs layer 3 of the metal buffer layer 4.

As shown in FIG. 2, the n type GaAs substrate applied to thesemiconductor light emitting device and the fabrication method for thesame according to the present embodiment includes: an n type GaAs layer6; a metal buffer layer 2 disposed on the surface of the n type GaAslayer 6; a metal layer 1 disposed on the metal buffer layer 2; a metalbuffer layer 4 disposed at the back side of the n type GaAs layer 6; anda metal layer 5 disposed on the surface of the opposite side at the sideof the n type GaAs layer 6 of the metal buffer layer 4.

In the structure of FIG. 1, each the metal layers 1 and 5 are formed ofan Au layer, and each the metal buffer layers 2 and 4 can be all formed,for example of an AuBe layer in order to achieve the electrical contactto the p type GaAs layer 3. Moreover, in the structure of FIG. 2, eachthe metal layers 1 and 5 are formed of an Au layer, and each the metalbuffer layers 2 and 4 can be formed, for example of an AuGe layer inorder to achieve the electrical contact to the n type GaAs layer 6.

As shown in FIG. 3, a schematic cross-section structure of the LEDapplied to the semiconductor light emitting device and the fabricationmethod for the same according to the present embodiment includes: ametal layer 12; a metallic contacts layer 11 disposed on the metal layer12; a p type cladding layer 10 disposed on the metallic contacts layer11; an MQW layer 9 disposed on the p type cladding layer 10; an n typecladding layer 8 disposed on the MQW layer 9; and a window layer 7disposed on the n type cladding layer 8.

In the structure of FIG. 3, the metal layer 12 is formed, for example ofan Au layer. Moreover, the metallic contacts layer 11 is formed, forexample of an AuBe layer or an alloy layer of AuBe and Ni. The p typecladding layer 10 is formed of an AlGaAs layer or a multilayer structureof an AlGaAs layer applying the conductivity type as p⁻ type and anAlGaAs layer applying the conductivity type as p⁺ type, for example, andthe thickness is about 0.1 μm, for example. The MQW layer 9 is composedof MQW (multi-quantum well) structure laminated by about 100 pairs ofheterojunction pairs composed of a GaAs/GaAlAs layer, for example, andthe thickness is formed in about 1.6 μm, for example. The n typecladding layer 8 is formed, for example of an n type AlGaAs layer, andthe thickness is about 0.1 μm, for example. The window layer 7 iscomposed, for example of a multilayer structure of an AlGaAs layer, anda GaAs layer formed on the multilayer structure of the AlGaAs layer, andthe whole thickness is about 0.95 μm.

As shown in FIG. 4, the semiconductor light emitting device according tothe present embodiment is formed by bonding mutually the LED structureshown in FIG. 3 with the p type GaAs substrate or the n type GaAssubstrate shown in FIG. 1 or FIG. 2 by the wafer bonding technology.

That is, as shown in FIG. 4, the semiconductor light emitting deviceaccording to the present embodiment is composed of: a p(n) type GaAssubstrate structure including the p (n) type GaAs layer 3 (6), the metalbuffer layer 2 disposed on the surface of the p (n) type GaAs layer 3(6), the metal layer 1 disposed on the metal buffer layer 2, the metalbuffer layer 4 disposed at the back side of the p (n) type GaAs layer 3(6), and the metal layer 5 disposed on the surface of the opposite sideat the side of the p (n) type GaAs layer 3 of the metal buffer layer 4(6); and an LED structure disposed on the aforementioned p(n) type GaAssubstrate, and including the metal layer 12, the metallic contacts layer11 disposed on the metal layer 12, the p type cladding layer 10 disposedon the metallic contacts layer 11, the MQW layer 9 disposed on the ptype cladding layer 10, the n type cladding layer 8 disposed on the MQWlayer 9, and the window layer 7 disposed on the n type cladding layer 8.

In order to solve the problem of the Sn diffusion from the Au—Sn alloylayer, the p(n) type GaAs substrate structure and the LED structurewhich is composed of epitaxial growth layer are bonded by using themetal layer 1 and the metal layer 12. Accordingly, it is possible toform the metallic reflecting layer which does not need a barrier metaland has a sufficient reflection factor. The metallic reflecting layer isbeforehand formed of the metal layer 12 disposed at the LED structureside. Since a mirror surface is formed of the interface between the ptype cladding layer 10 and the metal layer 12, the radiated light fromthe LED is reflected in the aforementioned mirror surface. Although themetallic contacts layer 11 is a layer for achieving the ohmic contact ofthe metal layer 12 and the p type cladding layer 10, the metalliccontacts layer 11 is intervened to the interface between the metal layer12 and the p type cladding layer 10, and forms a part of the mirrorsurface.

As shown in FIG. 4, the semiconductor light emitting device according tothe present embodiment can bond the metal layer 1 at the side of theGaAs substrate and the metal layer 12 at the side of the LED structurecomposed of the epitaxial growth layer by thermocompression bonding byforming both the metal layer 1 and the metal layer 12 with the Au layer.

The conditions of wafer bonding are about 250 degrees C. to 700 degreesC., for example, and are 300 degrees C. to 400 degrees C. preferable,and the pressure of thermocompression bonding is about 10 MPa to 20 MPa,for example.

According to the semiconductor light emitting device according to thepresent embodiment, since the metallic reflecting layer having theeffective optical reflection factor can be formed on the structure atthe side of the LED by using the metal layer 12 composed of Au, the highbrightness of LED can be achieved.

Second Embodiment

(Element Structure)

A schematic cross-section structure of an LED applied to a semiconductorlight emitting device and a fabrication method for the same according toa second embodiment of the present invention is expressed as shown inFIG. 5. Moreover, a schematic cross-section structure of an LED appliedto a semiconductor light emitting device a fabrication method for thesame according to a modified example of the present embodiment and isexpressed as shown in FIG. 6.

A schematic cross-section structure of a semiconductor light emittingdevice according to the present embodiment formed by the wafer bondingtechnology by bonding mutually the LED shown in FIG. 6 with the p typeor n type GaAs substrate 15 is expressed as shown in FIG. 7. Inaddition, in FIG. 7, the metal layer which is composed of Au layer forexample, and is disposed on the GaAs substrate 15 is omittingillustration. Alternatively, it is also possible to bond the GaAssubstrate 15 and the LED structure only by the metal layer 12, withoutdisposing metal layers, such as an Au layer, on the GaAs substrate 15.

As shown in FIG. 5, the LED applied to the semiconductor light emittingdevice and the fabrication method for the same according to the presentembodiment includes: a metal layer 12; a patterned metallic contactslayer 11 and a patterned insulating layer 17 disposed on the metal layer12; a p type cladding layer 10 disposed on the patterned metalliccontacts layer 11 and the patterned insulating layer 17; an MQW layer 9disposed on the p type cladding layer 10; an n type cladding layer 8disposed on the MQW layer 9; and a window layer 7 disposed on the n typecladding layer 8.

In the structure of FIG. 5, the metal layer 12 is formed, for example ofan Au layer, and the thickness is about 2.5 to 5 μm, for example.Moreover, the metallic contacts layer 11 is formed, for example of anAuBe layer or an alloy layer of AuBe and Ni, for example. The thicknessis the same grade as the insulating layer 17, for example, and is about450 nm. The insulating layer 17 is formed, for example of a silicondioxide film, a silicon nitride film, an SiON film, an SiO_(x)N_(y)film, or these multilayer films. The p type cladding layer 10 is formedof an AlGaAs layer or a multilayer structure of an AlGaAs layer applyingthe conductivity type as p⁻ type and an AlGaAs layer applying theconductivity type as p⁺ type, for example, and the thickness is about0.1 μm, for example. The MQW layer 9 is composed of an MQW(Multi-Quantum Well) structure which laminates about 100 pairs ofheterojunction pairs composed of a GaAs/GaAlAs layer, for example, andthe thickness is formed in about 1.6 μm, for example. The n typecladding layer 8 is formed, for example of an n type AlGaAs layer, andthe thickness is about 0.1 μm, for example. The window layer 7 iscomposed, for example of a multilayer structure of an AlGaAs layer, anda GaAs layer formed on the multilayer structure of the AlGaAs layer, andthe whole thickness is about 0.95 μm.

Modified Example of Second Embodiment

As shown in FIG. 6, the LED applied to the semiconductor light emittingdevice and a fabrication method for the same according to the modifiedexample of the present embodiment includes: a metal layer 12; a metalbuffer layer 18 disposed on the metal layer 12; a patterned metalliccontacts layer 11 and a patterned insulating layer 17 disposed on themetal buffer layer 18; a p type cladding layer 10 disposed on thepatterned metallic contacts layer 11 and the patterned insulating layer17; an MQW layer 9 disposed on the p type cladding layer 10; an n typecladding layer 8 disposed on the MQW layer 9; and a window layer 7disposed on the n type cladding layer 8.

In the structure of FIG. 6, the metal buffer layer 18 is formed, forexample of Ag, Al, Ni, Cr, or W layer. Since blue light and ultravioletlight are absorbed in the metal layer 12 composed of Au layer, it ispreferable to provide the metal buffer layer 18 composed of Ag, Al, etc.in order to reflect the light at the side of such short wavelength. Inthe structure of FIG. 6, since each layers except the metal buffer layer18 are formed as well as the structure of FIG. 5, the explanation isomitted.

The semiconductor light emitting device according to the presentembodiment is formed by bonding mutually the LED structure shown in FIG.5 to FIG. 6 and the GaAs substrate 15 by the wafer bonding technology,as shown in FIG. 7.

That is, as shown in FIG. 7, the semiconductor light emitting deviceaccording to the present embodiment is composed of: a GaAs substrate 15;a metal layer 12 disposed on the GaAs substrate 15; a metal buffer layer18 disposed on the metal layer 12; a patterned metallic contacts layer11 and a patterned insulating layer 17 disposed on the metal bufferlayer 18; a p type cladding layer 10 disposed on the patterned metalliccontacts layer 11 and the patterned insulating layer 17; an MQW layer 9disposed on the p type cladding layer 10; an n type cladding layer 8disposed on the MQW layer 9; and an LED structure including a windowlayer 7 disposed on the n type cladding layer 8.

It is possible to form the metallic reflecting layer having a sufficientreflection factor by bonding the GaAs substrate 15 and the LED structurecomposed of the epitaxial growth layer by using the metal layer 12. Themetallic reflecting layer is beforehand formed of the metal layer 12disposed at the LED structure side. Since a mirror surface is formed ofthe interface between the insulating layer 17, and the metal layer 12 orthe metal buffer layer 18, the radiated light from the LED is reflectedon the aforementioned mirror surface. Although the metallic contactslayer 11 is a layer for achieving the ohmic contact of the metal layer12 or the metal buffer layer 18, and the p type cladding layer 10, themetallic contacts layer 11 is intervened to the interface between themetal layer 12 and the p type cladding layer 10, and has the thicknessof the same grade as the insulating layer 17.

Since a substantial light emitting region is limited when the patternwidth of the metallic contacts layer 11 is wide, the area efficiencyreduces and the light emitting efficiency decreases. On the other hand,since the sheet resistivity of the metallic contacts layer 11 increasesand the forward voltage Vf of the LED rises when the pattern width ofthe metallic contacts layer 11 is narrow, the optimal pattern width andpattern structure exist. In some examples of a pattern, there is ahoneycomb pattern structure based on a hexagon or a dotted patternstructure based on a round shape. Such pattern shape will be explainedin relation to a fourth embodiment, referring to FIG. 13 and FIG. 14.

As shown in FIG. 4, as for the semiconductor light emitting devicerelated to the present embodiment, the metal layer (not shown) at theside of the GaAs substrate and the metal layer 12 at the side of the LEDstructure composed of the epitaxial growth layer can be bonded bythermocompression bonding by forming both the metal layer disposed on aGaAs substrate, and the metal layer 12 disposed at the LED side by theAu layer.

The conditions of wafer bonding are about 250 degrees C. to 700 degreesC., for example, and are 300 degrees C. to 400 degrees C. preferable,and the pressure of thermocompression bonding is about 10 MPa to 20 MPa,for example.

According to the semiconductor light emitting device according to thepresent embodiment, the contact between the semiconductor layer, such asthe p type cladding layer 10, and the metal layer 12 can be avoided, theoptical absorption can be prevented, and the metallic reflecting layerhaving a sufficient reflection factor can be formed by forming thetransparent insulating layer 17 between the metal layer 12 acting as themetallic reflecting layer or the metal buffer layer 18, and thesemiconductor layer, such as the p type cladding layer 10.

In order to perform patterning formation of the transparent insulatinglayer 17 and to achieve ohmic contact, the metallic contacts layer 11composed of AuBe etc. is vapor-deposited by lift off.

Then, the Au layer used for bonding with the GaAs substrate 15 on theinsulating layer 17 is vapor-deposited, and the metal layer 12 isformed.

According to the semiconductor light emitting device according to thepresent embodiment, the high brightness of LED can be achieved since thecontact the semiconductor layer, such as the p type cladding layer 10,with the metal layer 12 can be avoided, the optical absorption can beprevented, and the metallic reflecting layer having the sufficientreflection factor can be formed, by intervening the transparentinsulating layer 17 between the metallic reflecting layer and thesemiconductor layer.

Moreover, according to the semiconductor light emitting device accordingto the present embodiment, the light of short wavelength, such asultraviolet rays having a low reflection factor, can be efficientlyreflected on Au, and the high brightness of LED can be achieved byforming the metal buffer layer 18 composed of Ag, Al, etc. between theinsulating layer 17 and the metal layer 12.

Moreover, according to the semiconductor light emitting device accordingto the present embodiment, since the light is not absorbed in theinterface between the p type cladding layer and the metallic reflectinglayer, the high brightness of LED can be achieved.

Third Embodiment

(Element Structure)

A schematic cross-section structure of a GaAs substrate applied to asemiconductor light emitting device and a fabrication method for thesame according to a third embodiment of the present invention isexpressed as shown in FIG. 8. Moreover, a schematic cross-sectionstructure of an LED applied to the semiconductor light emitting deviceand a fabrication method for the same according to the presentembodiment is expressed as shown in FIG. 9.

A schematic cross-section structure of the semiconductor light emittingdevice according to the third embodiment of the present invention formedby bonding mutually the GaAs substrate 15 provided with the metal layer20 shown in FIG. 8 and the LED shown in FIG. 9 by the wafer bondingtechnology is expressed as shown in FIG. 10.

A p type or n type GaAs substrate structure applied to a semiconductorlight emitting device and the fabrication method for the same accordingto the present embodiment includes a GaAs substrate 15 and a metal layer20 disposed on the surface of the GaAs substrate 15, as shown in FIG. 8.

In the structure of FIG. 8, the metal layer 20 is formed, for example ofan Au layer.

As shown in FIG. 9, a schematic cross-section structure of the LEDapplied to the semiconductor light emitting device and the fabricationmethod for the same according to the present embodiment includes: ametal layer 12; a p type cladding layer 10 disposed on the metal layer12; an MQW layer 9 disposed on the p type cladding layer 10; an n typecladding layer 8 disposed on the MQW layer 9; and a window layer 7disposed on the n type cladding layer 8.

In the structure of FIG. 9, the metal layer 12 is formed, for example ofan Au layer, and the thickness is about 1 μm. Moreover, the p typecladding layer 10 is formed of an AlGaAs layer or a multilayer structureof an AlGaAs layer applying the conductivity type as p⁻ type and theAlGaAs layer applying the conductivity type as p⁺ type, for example, andthe whole thickness is formed in about 0.1 μm, for example. The MQWlayer 9 is composed of an MQW (Multi-Quantum Well) structure whichlaminates about 80 to 100 pairs of heterojunction pairs composed of aGaAs/GaAlAs layer, for example, and the whole thickness is formed inabout 1.6 μm, for example. The n type cladding layer 8 is formed, forexample of an n type AlGaAs layer, and the thickness is about 0.1 μm,for example. The window layer 7 is composed, for example of a multilayerstructure of an AlGaAs layer, and a GaAs layer formed on the multilayerstructure of the AlGaAs layer, and the whole thickness is about 0.95 μm.

As shown in FIG. 10, the semiconductor light emitting device accordingto the present embodiment is formed by bonding mutually the LEDstructure shown in FIG. 9 with the p type or n type GaAs substrate shownin FIG. 8 by the wafer bonding technology.

That is, as shown in FIG. 10, the semiconductor light emitting deviceaccording to the present embodiment is composed of: a GaAs substratestructure including the GaAs substrate 15, and the metal layer 20disposed on the surface of the GaAs substrate 15; and an LED structuredisposed on the aforementioned GaAs substrate structure and includingthe metal layer 12, the p type cladding layer 10 disposed on the metallayer 12, the MQW layer 9 disposed on the p type cladding layer 10, then type cladding layer 8 disposed on the MQW layer 9, and the windowlayer 7 disposed on the n type cladding layer 8.

The metallic reflecting layer is beforehand formed of the metal layer 12disposed at the LED structure side. Since a mirror surface is formed ofthe interface between the p type cladding layer 10 and the metal layer12, the radiated light from the LED is reflected in the aforementionedmirror surface.

As shown in FIG. 10, the semiconductor light emitting device accordingto the present embodiment can bond the metal layer 20 at the side of theGaAs substrate and the metal layer 12 at the side of the LED structurecomposed of the epitaxial growth layer by thermocompression bonding byforming both the metal layer 20 and the metal layer 12 with the Aulayer.

The conditions of wafer bonding are about 250 degrees C. to 700 degreesC., for example, and are 300 degrees C. to 400 degrees C. preferable,and the pressure of thermocompression bonding is about 10 MPa to 20 MPa,for example.

According to the semiconductor light emitting device and the fabricationmethod for the same according to the present embodiment, it has thecharacteristic at the point of performing total reflection of the lightby using the metal for the reflecting layer in order to prevent theoptical absorption to the GaAs substrate, and preventing the absorptionto the GaAs substrate. As a material of the semiconductor substrate tobond, non-transparent semiconductor substrate materials, such as GaAsand Si, are used.

The metal layer 20 and the metal layer 12 are bonding by using the Aulayer as the metal layer 20 at the side of the GaAs substrate 15 andusing the Au layer also as the metal layer 12 at the side of the LEDincluding the epitaxial growth layer, and the metal layer 12 used forbonding is applied to the optical reflecting layer as the metallicreflecting layer.

According to the semiconductor light emitting device and the fabricationmethod for the same according to the present embodiment, the highbrightness of the LED can be performed since it is possible to performtotal reflection of the light by using the metal for the reflectinglayer, to prevent the absorption to the GaAs substrate, and to reflectthe light of all angles, in order to prevent the optical absorption tothe GaAs substrate.

Fourth Embodiment

(Element Structure)

A schematic cross-section structure of a silicon substrate applied to asemiconductor light emitting device and a fabrication method for thesame according to a fourth embodiment of the present invention isexpressed as shown in FIG. 11. Moreover, a schematic cross-sectionstructure of an LED applied to the semiconductor light emitting deviceand a fabrication method for the same according to the presentembodiment is expressed as shown in FIG. 12. A schematic plane patternstructure of the LED applied to the semiconductor light emitting deviceand the fabrication method for the same according to the presentembodiment is expressed as shown in FIG. 13. Moreover, another schematicplane pattern structure is expressed as shown in FIG. 14.

As shown in FIG. 11, the silicon substrate 21 applied to thesemiconductor light emitting device and the fabrication method for thesame according to the present embodiment includes a silicon substrate21, a titanium (Ti) layer 22 disposed on the surface of the siliconsubstrate 21, and a metal layer 20 disposed on the surface of thetitanium (Ti) layer 22.

In the structure of FIG. 11, the thickness of the silicon substrate 21is about 130 μm, for example. The metal layer 20 is formed, for exampleof an Au layer, and the thickness is about 2.5 μm.

As shown in FIG. 12, the LED applied to the semiconductor light emittingdevice and the fabrication method for the same according to the presentembodiment includes: a GaAs substrate 23; an AlInGaP layer 24 disposedon the GaAs substrate 23; an n type GaAs layer 25 disposed on theAlInGaP layer 24; an epitaxial growth layer 26 disposed on the n typeGaAs layer 25; a patterned metallic contacts layer 11 and a patternedinsulating layer 17 disposed on the epitaxial growth layer 26; and ametal layer 12 disposed on the patterned metallic contacts layer 11 andthe patterned insulating layer 17.

In the structure of FIG. 12, the thickness of the GaAs substrate 23 isabout 300 μm, for example, and the thickness of the AlInGaP layer 24 isabout 350 nm, for example. Moreover, the n type GaAs layer 25 functionsas a contact layer between the GaAs substrate 23 and the epitaxialgrowth layer 26 via the AlInGaP layer 24, and the thickness is about 500nm, for example. The epitaxial growth layer 26 includes: an n typewindow layer composed of an AlGaAs layer; an n type cladding layer; anMQW layer composed of a plurality of pairs of the heterojunction ofGaAs/AlGaAs; an n type cladding layer composed of an AlGaAs layer; and ap type window layer composed of an AlGaAs layer/GaP layer. The MQW layeris composed of an MQW (Multi-Quantum Well) structure which laminatesabout 100 pairs of heterojunction pairs composed of a GaAs/GaAlAs layer,for example, and the thickness is formed in about 1.6 μm, for example.

Moreover, the metallic contacts layer 11 is formed, for example of anAuBe layer or an alloy layer of AuBe and Ni, for example. The thicknessis the same grade as the insulating layer 17, and is about 450 nm.

The metallic contacts layer 11 may be formed, for example as layeredstructure, such as Au/AuBe—Ni alloy/Au. The insulating layer 17 isformed, for example of a silicon dioxide film, a silicon nitride film,an SiON film, an SiO_(x)N_(y) film, or these multilayer films.

The metal layer 12 is formed, for example of an Au layer, and thethickness is about 2.5 to 5 μm, for example. The p type cladding layerin the epitaxial growth layer 26 is formed of an AlGaAs layer or amultilayer structure of an AlGaAs layer applying the conductivity typeas p⁻ type and an AlGaAs layer applying the conductivity type as p⁺type, for example, and the thickness is about 0.1 μm, for example. The ntype cladding layer in the epitaxial growth layer 26 is formed, forexample of a n type AlGaAs layer, and the thickness is about 0.1 μm, forexample. An n type window layer is composed, for example of a multilayerstructure of an AlGaAs layer and a GaAs layer formed on the multilayerstructure of the AlGaAs layer, and the whole thickness is about 0.95 μm,for example. A p type window layer is composed, for example of amultilayer structure of an AlGaAs layer and a GaP layer formed on themultilayer structure of the AlGaAs layer, and the whole thickness isabout 0.32 μm, for example.

As shown in FIG. 20, the semiconductor light emitting device accordingto the present embodiment is formed by bonding mutually the siliconsubstrate structure shown in FIG. 11, and the LED structure shown inFIG. 12 by the wafer bonding technology.

That is, as shown in FIG. 20, the semiconductor light emitting deviceaccording to the present embodiment includes: a silicon substratestructure composed of a silicon substrate 21, a titanium layer 22disposed on the silicon substrate 21, and a metal layer 20 disposed onthe titanium layer 22; and an LED structure composed of a metal layer 12disposed on the metal layer 20, a patterned metallic contacts layer 11and a patterned insulating layer 17 disposed on the metal layer 12, anepitaxial growth layer 26 disposed on the patterned metallic contactslayer 11 and the patterned insulating layer 17 and having a frostingprocessing region 30 (region formed by performing frosting processing ofthe exposed n type GaAs layer 25) on the exposed surface, a patterned ntype GaAs layer 25 disposed on the epitaxial growth layer 26, and apatterned surface electrode layer 29 disposed on the n type GaAs layer25 similarly. In addition, in the silicon substrate structure, atitanium layer 27 and a back surface electrode layer 28 are disposed atthe back side of the silicon substrate 21. Moreover, a blocking layer 31for preventing current concentration may be disposed between theepitaxial growth layer 26 and the n type GaAs layer 25, as shown in FIG.21 and FIG. 22 which are described later. As a material of the blockinglayer 31 in this case, GaAs can be applied, and the thickness is about500 nm, for example.

Also in the semiconductor light emitting device according to the presentembodiment, as shown in FIG. 20, it is possible to form a metallicreflecting layer having a sufficient reflection factor by bonding thesilicon substrate structure and the LED structure composed of theepitaxial growth layer by using the metal layer 12. The metallicreflecting layer is beforehand formed of the metal layer 12 disposed atthe LED structure side. Since a mirror surface is formed of theinterface between the insulating layer 17 and the metal layer 12, theradiated light from the LED is reflected in the aforementioned mirrorsurface. Although the metallic contacts layer 11 is a layer forachieving the ohmic contact of the metal layer 12 and the epitaxialgrowth layer 26, the metallic contacts layer 11 is intervened to theinterface between the metal layer 12 and the epitaxial growth layer 26,and has the thickness of the same grade as the insulating layer 17.

(Plane Pattern Structure)

Since a substantial light emitting region is limited when the patternwidth of the metallic contacts layer 11 is wide, the area efficiencyreduces and the light emitting efficiency decreases. On the other hand,when the pattern width of the metallic contacts layer 11 is narrow, thesheet resistivity of the metallic contacts layer 11 increases and theforward voltage Vf of LED rises. Accordingly, there are the optimalpattern width W and the pattern pitch D1. In some examples of thepattern, there is a honeycomb pattern structure based on a hexagon or acircular dotted pattern structure based on a circular dotted shape basicstructure.

A schematic plane pattern structure of the LED applied to thesemiconductor light emitting device and the fabrication method for thesame according to the present embodiment has the honeycomb patternstructure based on a hexagonal basic structure, for example, as shown inFIG. 13. In FIG. 13, the shaped part shown by the width W shows apattern of the metallic contacts layer 11 formed, for example of an AuBelayer or an alloy layer of AuBe and Ni also in FIG. 12. The hexagonalpattern having the width D1 is equivalent to a part of the insulatinglayer 17, and expresses a region where the radiated light from LED isguided. The width D1 is about 100 μm, for example, and the line width Wis about 5 μm to about 11 μm.

Another schematic plane pattern structure of the LED applied to thesemiconductor light emitting device and the fabrication method for thesame according to the present embodiment has a dotted pattern structurebased on a round shape, for example, as shown in FIG. 14. In FIG. 14,the shaped part shown by the width d shows a pattern of the metalliccontacts layer 11 formed of an AuBe layer or an alloy layer of AuBe andNi in FIG. 12, and is disposed by the pattern pitch having the width D2.In FIG. 14, the region except the circular pattern part having the widthd and the pattern pitch D2 is equivalent to a part of the insulatinglayer 17, and expresses a region where the radiated light from LED isguided. The pattern pitch D2 is about 100 μm, for example, and the widthd is about 5 μm to about 11 μm.

The schematic plane pattern structure of the LED applied to thesemiconductor light emitting device the fabrication method for the sameaccording to the present embodiment and is not limited to the hexagonalhoneycomb pattern and the circular dotted pattern, but a random patternfor disposing a triangular pattern, a rectangular pattern, a hexagonalpattern, an octagonal pattern, a circular dotted pattern, etc. at randomis also applicable.

The schematic plane pattern structure of the LED applied to thesemiconductor light emitting device according to the present embodimenthas only to be able to secure the metal wiring pattern width which is alevel in which the forward voltage Vf of LED does not rise withoutreducing the light emitting brightness from the LED securing the size ofa light guide region.

(Fabrication Method)

The fabrication method of the semiconductor light emitting deviceaccording to the present embodiment will be explained hereinafter.

Schematic cross-section structures for explaining one process of thefabrication method of the semiconductor light emitting device accordingto the present embodiment is expressed as shown in FIG. 11 to FIG. 20.

(a) First of all, a silicon substrate structure for wafer bonding isprepared as shown in FIG. 11, and an LED structure for wafer bonding isprepared as shown in FIG. 12. In the silicon substrate structure, thetitanium layer 22 and the metal layer 20 composed of Au, etc. are formedone after another using a spattering technique, a vacuum evaporationtechnique, etc. on the silicon substrate 21. In the LED structure, theAlInGaP layer 24 on the GaAs substrate 23, the n type GaAs layer 25, andthe epitaxial growth layer 26 are formed one after another using an MBE(Molecular Beam Epitaxy) method, an MOCVD (Metal Organic Chemical VaporDeposition) method, etc. Next, the metallic contacts layer 11 and themetal layer 12 are formed for the patterned insulating layer 17 on theepitaxial growth layer 26 by using a lift off method.(b) Next, as shown in FIG. 15, the silicon substrate structure for waferbonding shown in FIG. 11, and the LED structure for wafer bonding shownin FIG. 12 are bonded. In the bonding process, it performs on theconditions for about 340 degrees C. as a thermocompression bondingtemperature, about 18 MPa as a thermocompression bonding pressure, andabout 10 minutes as thermocompression bonding time, by using a pressingmachine, for example.(c) Next, as shown in FIG. 16, the titanium layer 27 and the backsurface electrode layer 28 composed of Au, etc. are formed for the backside of the silicon substrate 21 one after another using a spatteringtechnique, a vacuum evaporation technique, etc. When not making thetitanium layer 27 intervene between the Au layer and the siliconsubstrate 21, Au of the joined part between the silicon substrate 21 andthe Au layer becomes AuSi silicide and the reflection factor is reducedif sintering is performed in order to achieve the ohmic contact.Therefore, the titanium layer 27 is a metal for bonding the siliconsubstrate 21 with the Au layer. In order to prevent AuSi siliciding,tungsten (W) is needed as a barrier metal, and it is necessary to form ametal layer by silicon substrate/Ti/W/Au from the substrate side as astructure at that time.(d) Next, as shown in FIG. 17, after protecting the back surfaceelectrode layer 28 by resist etc., the GaAs substrate 23 is removed byetching. The etching time is about 65 to 85 minutes by using the etchingsolution consisting of ammonia/hydrogen peroxide solution, for example.Here, the AlInGaP layer 24 performs an important function as an etchingstopper.(e) Next, as shown in FIG. 18, the AlInGaP layer 24 is removed by usinga hydrochloric acid based etching solution. The etching time is about 1minute and a half, for example.(f) Next, as shown in FIG. 19, the surface electrode layer 29 ispatterned after formation using a spattering technique, a vacuumevaporation technique, etc. The pattern of the surface electrode layer29 is substantially matched with the pattern of the metallic contactslayer 11. A layered structure composed of Au/AuGe—Ni alloy/Au, forexample can be used as a material of the surface electrode layer 29.Here, the n type GaAs layer 25 has a removal preventing function for thesurface electrode layer 29.(g) Next, as shown in FIG. 20, the n type GaAs layers 25 except n typeGaAs layer 25 directly under the surface electrode layer 29 is removedby performing frosting processing. As conditions for frostingprocessing, it can carry out by a nitric acid-sulfuric acid basedetching solution of about 30 degrees C. to 50 degrees C. and timeperiods of about 5 seconds to about 15 seconds, for example. Inaddition, the GaO₂ film formed on the surface is removable by etchingthe n type GaAs layer 25 as preprocessing of the frosting processingusing the thin liquid of fluoric acid. As the etching time, it is about3 minutes, for example.

In addition, a tungsten (W) barrier metal, a platinum (Pt) barriermetal, etc. can also be used as an alternative of the titanium layer 22and the titanium layer 27, for example.

According to the above explanation, as shown in FIG. 20, thesemiconductor light emitting device according to the fourth embodimentof the present invention using the silicon substrate 21 is completed.

Modified Example of Fourth Embodiment

A schematic cross-section structure for explaining one process of afabrication method of a semiconductor light emitting device according toa modified example of the present embodiment is expressed as shown inFIG. 21. Moreover, a schematic cross-section structure for explainingone process of a fabrication method of a semiconductor light emittingdevice according to another modified example of the present embodimentis expressed as shown in FIG. 22.

The semiconductor light emitting device according to the modifiedexample of the present embodiment is formed by bonding mutually asilicon substrate structure shown in FIG. 11 and an LED structure shownin FIG. 12 by the wafer bonding technology, as shown in FIG. 21.

That is, as shown in FIG. 20, the semiconductor light emitting deviceaccording to the present embodiment includes: a GaAs substrate structurecomposed of a GaAs substrate 15, a metal buffer layer (AuGe—Ni alloylayer) 32 disposed on the GaAs substrate 15, and a metal layer (Aulayer) 33 disposed on the metal buffer layer 32; and an LED structurewhich composed of a metal layer 12 disposed on the metal layer 33, apatterned metallic contacts layer 11 and a patterned insulating layer 17disposed on the metal layer 12, an epitaxial growth layer 26 disposed onthe patterned metallic contacts layer 11 and the patterned insulatinglayer 17 and having a frosting processing region 30 (region formed byperforming frosting processing of the exposed n type GaAs layer 25) onthe exposed surface, a patterned n type GaAs layer 25 disposed on theepitaxial growth layer 26, and a patterned surface electrode layer 29disposed on the n type GaAs layer 25 similarly. In addition, in the GaAssubstrate structure, a metal buffer layer (AuGe—Ni alloy layer) 34 and aback surface electrode layer 35 are disposed at the back side of theGaAs substrate 15. Moreover, as shown in FIG. 22, a blocking layer 31for preventing current concentration may be disposed between theepitaxial growth layer 26 and the n type GaAs layer 25. As a material ofthe blocking layer 31 in this case, GaAs can be applied and thethickness is about 500 nm, for example.

Also in the semiconductor light emitting device according to themodified example of the present embodiment, as shown in FIG. 21, it ispossible to form a metallic reflecting layer having a sufficientreflection factor by bonding the GaAs substrate structure and the LEDstructure composed of epitaxial growth layer, by using the metal layer12. The metallic reflecting layer is beforehand formed of the metallayer 12 disposed at the LED structure side. Since a mirror surface isformed of the interface between the insulating layer 17 and the metallayer 12, the radiated light from the LED is reflected in theaforementioned mirror surface. Although the metallic contacts layer 11is a layer for achieving the ohmic contact of the metal layer 12 and theepitaxial growth layer 26, the metallic contacts layer 11 is intervenedto the interface between the metal layer 12 and the epitaxial growthlayer 26, and has the thickness of the same grade as the insulatinglayer 17.

In the structure of FIG. 21 and FIG. 22, the metal buffer layer 34formed at the back side of the GaAs substrate 15 is formed, for exampleof an AuGe—Ni alloy layer, and the thickness is about 100 nm. Moreover,the back surface electrode layer 35 is formed of an Au layer, and thethickness is about 500 nm. The metal buffer layer 32 formed on thesurface of the GaAs substrate 15 is formed, for example of an AuGe—Nialloy layer, and the thickness is about 100 nm. Furthermore, the metallayer 33 is formed of an Au layer, and the thickness is about 1 μm.

Since each process of the fabrication method of the semiconductor lightemitting device according to the present embodiment shown in FIG. 11 toFIG. 20 is the same also in the fabrication method of the semiconductorlight emitting device according to the modified example of the presentembodiment, the explanation is omitted.

A schematic plane pattern structure of LED applied to the semiconductorlight emitting device and the fabrication method for the same accordingto the modified example of the present embodiment can also apply thesame structure as FIG. 13 or FIG. 14.

It is also available to form the metal buffer layer 18 (refer to FIG. 6)composed of Ag, Al, etc. between the insulating layer 17 and the metallayer 12 explained in the modified example of the second embodiment,also in the semiconductor light emitting device according to the presentembodiment and its modified example. It is because the light of shortwavelength, such as ultraviolet rays having a low reflection factor, canbe efficiently reflected at Au by forming the metal buffer layer 18composed of Ag, Al, etc.

According to the semiconductor light emitting device according to thepresent embodiment and its modified example, and the fabrication methodfor the same, the high brightness of LED can be achieved since thecontact with the epitaxial growth layer 26 and the metal layer 12 can beavoided, the optical absorption can be prevented, and the metallicreflecting layer having a sufficient reflection factor can be formed byintervening the transparent insulating layer 17 between the metallicreflecting layer and the semiconductor layer.

Moreover, according to the semiconductor light emitting device accordingto the present embodiment and its modified example, and the fabricationmethod for the same, the light of short wavelength, such as ultravioletrays having a low reflection factor, can be efficiently reflected at Au,and the high brightness of the LED can be achieved, by forming the metalbuffer layer composed of Ag, Al, etc. between the insulating layer 17and the metal layers 12 and 20.

Moreover, according to the semiconductor light emitting device accordingto the present embodiment and its modified example, and the fabricationmethod for the same, the high brightness of the LED can be achievedsince the contact with the epitaxial growth layer 26 and the metal layer12 is avoided and the light is not absorbed in the interface between theepitaxial growth layer 26 and the metallic reflecting layer.

According to the semiconductor light emitting device according to thepresent embodiment and its modified example, and the fabrication methodfor the same, the high brightness of the LED can be performed since itbecomes possible to perform the total reflection of the light by usingthe metal for the reflecting layer in order to prevent the opticalabsorption to the silicon substrate or the GaAs substrate, to preventthe absorption to the silicon substrate or the GaAs substrate, and toreflect the light of all angles.

Other Embodiments

The present invention has been described by the first to fourthembodiments, as a disclosure including associated description anddrawings to be construed as illustrative, not restrictive. With thedisclosure, artisan might easily think up alternative embodiments,embodiment examples, or application techniques.

In the semiconductor light emitting device and the fabrication methodfor the same according to the first to fourth embodiment, although thesilicon substrate and the GaAs substrate are mainly explained to theexample as the semiconductor substrate, it is available enough in GeSiGe, SiC, GaN substrate, or a GaN epitaxial substrate on SiC.

Although the LED is mainly explained to the example as the semiconductorlight emitting device according to the first to fourth embodiment, an LD(Laser Diode) may be composed, and in that case, a DFB (DistributedFeedback) LD, a DBR (Distributed Bragg Reflector) LD, a VCSEL (VerticalCavity Surface Emitting Laser Diode), etc. may be composed.

Such being the case, the present invention covers a variety ofembodiments, whether described or not. Therefore, the technical scope ofthe present invention is appointed only by the invention specific matterrelated appropriate scope of claims from the above-mentionedexplanation.

According to the semiconductor light emitting device and the fabricationmethod for the same according to the present invention, the highbrightness of the LED can be achieved since the barrier metal becomesunnecessary by bonding the epitaxial growth layer and the semiconductorsubstrate by using the metal layer composed of Au in order to solve theproblem of Sn diffusion by Au—Sn alloy layer, and the metallicreflecting layer having a sufficient optical reflection factor can beformed in the structure at the side of the LED by using the metal layercomposed of Au.

According to the semiconductor light emitting device and the fabricationmethod for the same according to the present invention, the highbrightness of the LED can be achieved since the contact with thesemiconductor layer and the metallic reflecting layer can be avoided,the optical absorption in the interface between the semiconductor layerand the metallic reflecting layer can be prevented, and the metallicreflecting layer having a sufficient reflection factor can be formed, byinserting the transparent insulating film between the metallicreflecting layer and the semiconductor layer.

According to the semiconductor light emitting device, and thefabrication method for the same according to the present invention, thehigh brightness of the LED can be performed since it is possible toperform the total reflection of the light by using the metal for thereflecting layer in order to prevent the optical absorption to the GaAssubstrate, to prevent the absorption to the GaAs substrate, and toreflect the light of all angles.

INDUSTRIAL APPLICABILITY

The semiconductor light emitting device and the fabrication method forthe same according to the embodiments of the invention can be used forwhole semiconductor light emitting devices, such as an LED device havinga non-transparent substrate, such as a GaAs substrate and a Sisubstrate, and an LD device.

The invention claimed is:
 1. A semiconductor light emitting devicecomprising: a semiconductor substrate comprising a first surface and asecond surface, the second surface opposite to the first surface; afirst metal layer formed on the first surface, the first metal layercontaining Au; a second metal layer formed on the first metal layer, thesecond metal layer containing Au; an epitaxial growth layer formed onthe second metal layer, the epitaxial growth layer containing Ga; and afirst electrode layer disposed over the epitaxial growth layer such thata portion of the epitaxial growth layer is exposed in a plan view, thefirst electrode layer containing Au, wherein the exposed portion of theepitaxial growth layer comprises an uneven portion.
 2. The semiconductorlight emitting device according to claim 1, wherein a height of theuneven portion is lower than the first electrode layer.
 3. Thesemiconductor light emitting device according to claim 1, wherein theuneven portion is a frosting processing region.
 4. The semiconductorlight emitting device according to claim 1, further comprising an n typeGaAs layer formed on the epitaxial growth layer apart from the exposedportion of the epitaxial growth layer, wherein the first electrode layeris formed on the n type GaAs layer and coextensive therewith in the planview.
 5. The semiconductor light emitting device according to claim 1,wherein the semiconductor substrate side and the epitaxial growth layerside are bonded to each other by bonding the first metal layer and thesecond metal layer.
 6. The semiconductor light emitting device accordingto claim 1, wherein the semiconductor substrate is a silicon substrate.7. The semiconductor light emitting device according to claim 1, furthercomprising a second electrode layer disposed on the second surface ofthe semiconductor substrate.
 8. The semiconductor light emitting deviceaccording to claim 1, further comprising a metal buffer layer disposedon the second metal layer, the metal buffer layer containing Ag.
 9. Asemiconductor light emitting device comprising: a semiconductorsubstrate comprising a first surface and a second surface, the secondsurface opposite to the first surface; a first metal layer formed on thefirst surface, the first metal layer containing Au; a second metal layerformed on the first metal layer, the second metal layer containing Au;an epitaxial growth layer formed on the second metal layer, theepitaxial growth layer containing Ga; and a first electrode layerdisposed over the epitaxial growth layer such that a portion of theepitaxial growth layer is exposed in a plan view, the first electrodelayer containing Au, wherein a surface of the epitaxial growth layerexposed from the first electrode layer in the plan view is rougher thana surface of the epitaxial growth layer covered by the first electrodelayer in the plan view.
 10. The semiconductor light emitting deviceaccording to claim 9, wherein the uneven portion is a frostingprocessing region.
 11. The semiconductor light emitting device accordingto claim 9, further comprising an n type GaAs layer formed on theepitaxial growth layer apart from the exposed portion of the epitaxialgrowth layer, wherein the first electrode layer is formed on the n typeGaAs layer and coextensive therewith in the plan view.
 12. Thesemiconductor light emitting device according to claim 9, wherein thesemiconductor substrate side and the epitaxial growth layer side arebonded to each other by bonding the first metal layer and the secondmetal layer.
 13. The semiconductor light emitting device according toclaim 9, wherein the semiconductor substrate is a silicon substrate. 14.The semiconductor light emitting device according to claim 9, furthercomprising a second electrode layer disposed on the second surface ofthe semiconductor substrate.
 15. The semiconductor light emitting deviceaccording to claim 9, further comprising a metal buffer layer disposedon the second metal layer, the metal buffer layer containing Ag.